There are several previous disclosures describing multihull ships having connections which enable relative movements between hulls.
Some prior constructions consider the use of resilient suspension blocks. Such means are efficient for shock absorbing, but not for providing better dynamic stabilities of ships at sea. For an improved stability, movements between hulls in accordance with the sizes of the waves at sea are necessary.
Regarding prior constructions with pivoting arms, which enable movements between hulls of large amplitudes, the difficulty arises from the fact that such prior constructions consider movements which are controlled by hydraulic cylinders, mechanical stops, set screws, or other mechanisms that provide clearly defined relative movements or clearly defined end positions of such movements.
The use of complex mechanisms for transmitting movements between hulls, rigid stops, or bulky constructions without resilient restoring members cannot sufficiently ballance the movements between hulls with all kinds and velocities of sea waves.
This invention provides a simple and comparatively small arrangement of pivoting arms and spring means, which improves the seaworthiness of a multihull ship and enables quick acceleration and high speeds.
This invention enables very large relative movements of the hulls of a ship, both in the pitch and in the heave modes. Movements in pitch mode are important because the different hulls of a multihull ship at sea will meet the waves at different points and with different slopes. Movements in heave are important because the waves, at different points of the ship, will have differents heights.
Previous constructions also have the shortcomings of providing interrelated motions.
With pivoting axes parallel to the length of the ship, each time such arms swing up and down, they also swing close to or away from the hulls, meaning that relative movements in heave are interrelated with relative and simultaneous movements in sway. With pivoting axes at right angles to the length of the ship, each time the arms swing up and down, they also swing forwards and backwards, meaning that relative movements in heave are interrelated with relative and simultaneous movements in surge.
This invention solves this problem because each one of the connections between hulls is made by at least two arms having the free ends interconnected with bearings which are not firmly secured in any particular position. Short arms can be used for producing movements in any direction and such movements may have large amplitudes. Such short arms and the simple direct movements in accordance with the direction of the forces of the waves provide significantly better frequency responses than bulkier constructions and interrelated movements.
Another drawback of previously disclosed structures with pivoting arms is related to the fact that the movements and relative positions of the hulls of such ships are defined by means of hydraulic cylinders, mechanical stops or other mechanisms.
Ships in which several hulls are forced into simultaneous motions are not ideal because much large masses have to be accelerated. The reaction is significantly slower than if each hull of a ship can move independently.
In this invention, better frequency responses are achieved because the springs will not force any hull to move in any particular direction each time a wave is forcing another hull of the same ship to heave and pitch in accordance with the forces produced by that wave.
The present invention is useful.
Conventional ships, to be really seaworthy and to have an acceptable drag, have to be very large and slow. Preferably over 40,000 tons deadweight, with speeds under 30 knots. Such large and slow vessels are only convenient for the transportation of raw materials and other goods that are traded in huge quantities. On land, transportation by rail or road takes place at speeds and volumes which are much more convenient.
At sea, surface effect ships are capable of such speeds, but have various shortcomings. Lift forces provided by air are not convenient for large vehicles. Surfaces become too large. This is also true for airplanes. Typically, commercial airplanes have payloads of less than 120 tons and cruising speeds just below the speed of sound. For increased payloads, wings or larger sizes would be necessary. As such larger wings are of heavier constructions, there is a limit above which it becomes impossible to build larger aircraft, unless supersonic speeds are adopted. But such high speeds are neither economic nor convenient for short and medium distances which are the ones that require mass transportation.
If lift force is produced by water instead of air, it becomes easy to build very large vehicles. The present invention enables the construction of ships with payloads between 1200 and 4000 tons and cruising speeds between 150 and 250 knots. Such ships will be very convenient for the average type of traffic.
For speeds under 30 knots, monohull ships have less drag than multihull ships. But, whenever seakeeping qualities are more important than the relation between weight and drag, the invention enables the construction of light deplacement ships having seakeeping qualities superior to the ones of much larger monolithic (monohull or multihull) ships.